#include <iostream>
#include <fstream>

using namespace std;
const char InFile[]="fractii.in";
const char OutFile[]="fractii.out";
const int DIMN=1000005;

ifstream in(InFile);
ofstream out(OutFile);
int v[DIMN];

int main()
{
    int sum,n;
    in>>n;
    for(int i=1;i<=n;++i)
        v[i]=0;
    sum=2*n-1;
    for(int i=2;i<=n;++i)
    {
        if(v[i]==0)
        {
            sum+=2*(n-i+1-n/i);
            for(int j=i+i;j<=n;j+=i)
                 v[j]=1;
        }
    }
    out << sum <<endl;
    return 0;
}